Track regulators are may be used, e.g., in power supply systems including separate voltage supplies at, e.g., the same voltage.
For instance, separate voltages may facilitate decoupling a main supply (as used, e.g., by a microcontroller) and ancillary supplies (e.g., sensor supplies) that may be fed outside the controller board and may be exposed to short circuits.
A track regulator is a kind of regulator whose voltage follows (or “tracks”) the voltage of another regulator to provide a separate voltage supply at, e.g., a same voltage thus acting, e.g., as a power buffer.
A soft-start function during track regulator start-up may be beneficial in order to limit inrush current and overshoot voltage at output. A voltage supply overshoot may cause, e.g., sensor/load damages. Also, an uncontrolled voltage slope may cause inrush current and destroy some parts of load.
Certain factors may affect implementing such a soft-start function for a track regulator.
For instance, the error amplifier in the track regulator may use a N-channel input pair and the input range of a N-channel input amplifier cannot be (too) close to the ground rail.
Also, the feedback loop of a track regulator with an N-channel input pair may be effective only when the output voltage is higher than a certain voltage (e.g., one VGS voltage).
Implementing a soft-start function in a track regulator working in a 5V range may thus be faced with various critical aspects.
Soft-start may be implemented via a digital-to-analog (D/A or D2A) converter that controls the input reference voltage used by regulator. Such a solution may be expensive, e.g., in terms of area, this being particularly the case when soft-start functions are implemented for many track regulators.